Schools could remain closed until we know how much children contribute to spreading coronavirus, England's chief medical officer has explained.
Professor Chris Whitty said understanding the transmission among children is a "very important" factor in deciding whether school closures are a "critical part of our long term response".
He made the stark admission at the end of an online Gresham College lecture last night as he highlighted the "many things we do not know, and need to" about the virus.
He said: "It's important that we don't know how much children contribute to transmitting the virus and this is very important for example in deciding whether school closures are a critical part of our long term response."
It was reported earlier in the week that Britain's schoolchildren could be back to school part-time before the summer holidays.
Education Secretary Gavin Williamson is planning a potential phased return to school for all pupils following the coronavirus lockdown but declined to give a date for them reopening.
But some reports claim the year groups with the most pressing educational milestones like exams could be prioritised.
The Sun reports youngsters about to make the move from primary school to secondary school, and pupils doing GCSEs or A Levels could get priority.
The UK could also see staggered return dates, with ministers' plans said to include strategies including allowing primary school children back first, followed by secondary pupils later.
A source told the newspaper that the Government was eager for children to return to school by summertime.
But these reports differ from Prof Whitty's comments made last night.
During the lecture Prof Whitty also said that a second wave of coronavirus could be "more severe" than the first and may spread more rapidly if it arrives in winter.
He said every country seeking to ease lockdown measures now must negotiate an "extremely difficult balancing act" to keep the pandemic under control.
In particular, the virus reproduction "R" number must be kept below one - meaning each infected person could expect to pass it to fewer than one other person on average.
Prof Whitty said: "We need to make sure that R does not go back above one. Because if not we will go back to a second wave.
"It is entirely plausible for a second wave to actually be more severe than the first if it is not mitigated.
"Every country has got an extremely difficult balancing act, and we all need to be honest about the fact there are no easy solutions here.
"Covid-19 is a very long way from finished and eradication is technically impossible for this disease."
